1. Field of the Invention
The present invention relates to a communication device, a communication method and a communication system, and in particular, to a communication device, a communication method and a communication system able to achieve a reduction in size and lowering of the costs of a wireless tag while ensuring security with regard to the wireless tag such as an IC card or an IC chip which performs, for example, proximity communication with a reader/writer.
2. Description of the Related Art
In recent years, proximity communication, where wireless communication is performed without contact at a close distance using IC (Integrated Circuit) cards or the like, is used for, for example, electronic commuter tickets, electronic money and the like, and also, mobile phone devices, which have an electronic commuter ticket or electronic money function using proximity communication, are in widespread use.
Proximity communication has been standardized as, for example, ISO/IEC 14443 or ISO/IEC 18092 (referred to below as NFC (Near Field Communication)).
Here, out of communication devices which perform proximity communication such as communication based on an NFC standard, a communication device such as an IC card or an IC chip, which performs proximity communication with a reader/writer, which outputs an RF (Radio frequency) signal, in a format of responding to the signal from a reader/writer, is referred to as a wireless tag.
For example, the wireless tag provides various types of services by having a non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) built in, and performing reading and writing data, which is exchanged with the reader/writer using proximity communication, in the non-volatile memory.
In the reader/writer and wireless tag, to prevent tampering of data stored in the non-volatile memory which is built into the wireless tag by proximity communication being performed with a fraudulent device, mutual authentication is performed, for example, in accordance with a symmetrical cipher algorithm (for example, Japanese Unexamined Patent Application Publication No. 2009-276916).
In the mutual authentication in accordance with a symmetrical cipher algorithm, one out of the reader/writer and the wireless tag, for example, the reader/writer, generates a random number RA, and by encrypting the random number RA using a common key KA, encryption data {RA}KA of the random number RA is generated and sent to the wireless tag.
The wireless tag receives the encryption data {RA}KA from the reader/writer and decrypts the encryption data {RA}KA using the common key KA. Furthermore, by encrypting the decryption result RA′ of the encryption data {RA}KA using a common key KB, encryption data {RA′}KB of the decryption result RA′ is generated and sent to the reader/writer by the wireless tag.
The reader/writer receives the encryption data {RA′}KB from the wireless tag and decrypts the encryption data {RA′}KB using the common key KB. Then, the reader/writer performs authentication of whether or not the wireless tag is a legitimate device by comparing the decryption result RA″ of the encryption data {RA′}KB and the random number RA.
That is, in a case where the decryption result RA″ of the encryption data {RA′}KB and the random number RA match with each other, since the wireless tag has the common keys KA and KB, the reader/writer recognizes that the wireless tag is a legitimate device (authentication of the wireless tag is successful).
In addition, in the mutual authentication in accordance with a symmetrical cipher algorithm, the other out of the reader/writer and the wireless tag, for example, the wireless tag, generates a random number RB, and by performing processing in the same manner as the case below where the reader/writer authenticates the wireless tag, the wireless tag performs authentication of whether or not the reader/writer is a legitimate device.
Then, when the authentication of the reader/writer is successful in the wireless tag, in the reader/writer and the wireless tag, an encryption key is generated using the random numbers RA and RB, data is encrypted using the encryption key, and data exchange is performed.
Accordingly, between the reader/writer and the wireless tag where mutual authentication has been successful, since the encryption data obtained by encrypting the data using the encryption key is exchanged, it is possible to prevent eavesdropping of the data.